Complexes of heterocyclic thione donors

Although self-assembled monolayers (SAMs) of alkylthiols on planar gold (2D SAMs) and on gold nanoparticles (3D SAMs) have been intensely studied, the actual nature of the Au−S bonding remains poorly characterized. Comparison of the X-ray photoelectron spectroscopy (XPS) spectra of 2D and 3D SAMs and “reference” Au(I) complexes, sometimes referred to as Au(I) thiolate polymers, provides detailed insight into this problem. We report high-resolution XPS spectra and Au 4f7/2 and S 2p3/2 binding energies (BE) in 2D SAMs, 3D SAMs and the Au(I) thiolate complexes for two short-chain thiols (n-C4SH and n-C5SH). Sulfur 2p3/2 BE shifts are used to compare the different states of bonding in the SAM systems and the Au(I) complexes and establish that the S atom in the SAM systems bears a charge of about 0.2e. The 2D and 3D SAMs exhibit similar XPS characteristics and are both distinguishable from the Au(I) complexes. The origins of the observed BE values are discussed in the context of the nature of the gold substrat...

Gold−Sulfur Bonding in 2D and 3D Self-Assembled Monolayers: XPS Characterization

A practical route is introduced for synthesizing a sulfur-impregnated graphene composite as a promising cathode material for lithium–sulfur batteries. Sulfur particles with a size of a few microns are successfully grown in the interior spaces between randomly dispersed graphene sheets through a heterogeneous crystal growth mechanism. The proposed route not only enables the control of the particle size of active sulfur but also affords quantitative yields of composite powder in large quantities. We investigate the potential use of the sulfur-impregnated graphene composite as a cathode material owing to its advantages of confining active sulfur, preventing the dissolution of soluble polysulfides, and providing sufficient electrical conduction. A high discharge capacity of 1237 mA h g−1 during the first cycle and a good cyclic retention of 67% after 50 cycles are attained in a voltage range of 1.8–2.6 V vs. Li/Li+. These results emphasize the importance of tailoring cathode materials for improving the electrochemical properties of lithium–sulfur batteries. Our results provide a basis for further investigations on advanced lithium batteries.

One-step synthesis of a sulfur-impregnated graphene cathode for lithium-sulfur batteries.

The ligand chemistry of tellurium

Molecular Co2+ ions were grafted onto doped graphene in a coordination environment, resulting in the formation of molecularly well-defined, highly active electrocatalytic sites at a heterogeneous interface for the oxygen evolution reaction (OER). The S dopants of graphene are suggested to be one of the binding sites and to be responsible for improving the intrinsic activity of the Co sites. The turnover frequency of such Co sites is greater than that of many Co-based nanostructures and IrO2 catalysts. Through a series of carefully designed experiments, the pathway for the evolution of the Co cation-based molecular catalyst for the OER was further demonstrated on such a single Co-ion site for the first time. The Co2+ ions were successively oxidized to Co3+ and Co4+ states prior to the OER. The sequential oxidation was coupled with the transfer of different numbers of protons/hydroxides and generated an active Co4+═O fragment. A side-on hydroperoxo ligand of the Co4+ site is proposed as a key intermediate f...

R.A. Walton

Papers

The x-ray photoelectron spectra of metal complexes of sulfur-containing ligands: sulfur 2p binding energies

Coordination complexes of the thallium(III) halides and their behavior in non-aqueous media

The x-ray photoelectron spectra of metal halides and their complexes: halogen binding energies and their correlation with structure